An intake apparatus including a distribution passage which distributes external gas to plural intake pipes is known. Such intake apparatus is disclosed in, for example, JP2014-137048A which is hereinafter referred to as Reference 1.
Reference 1 discloses a flow passage configuration for an internal combustion engine, the flow passage configuration including an exhaust gas recirculation (EGR) passage provided at an intake manifold which includes plural intake passages for respective cylinders of the internal combustion engine. In the flow passage configuration disclosed in Reference 1, the EGR passage (distribution passage) includes a tournament-type flow passage configuration. The EGR passage is connected to each of the intake passages so that EGR gas is distributable to each of the plural intake passages. The EGR passage in the tournament-type includes a first passage (first gas passage) which extends to one side in a horizontal direction (in a first horizontal direction) and includes a closed end at a tip end portion in the first horizontal direction and a communication bore (second gas passage) which extends in a vertical direction and is connected to the first passage at an upstream side relative to the closed end, i.e., at the other side in the horizontal direction (in a second horizontal direction). The EGR passage also includes a second passage and a third passage connected to a downstream end of the communication bore and branched to the second horizontal direction and the first horizontal direction, respectively, from the downstream end of the communication bore.
In the aforementioned flow passage configuration according to Reference 1, because of the closed end of the first passage, the volume of the EGR gas (external gas) directly flowing to the communication bore from the first passage decreases. Accordingly, the volume of the EGR gas flowing by inertia to the third passage (third gas passage) where the EGR gas flows in the same flow direction as the flow direction of the EGR gas at the first passage (i.e., in the first horizontal direction) decreases. As a result, the volume of the EGR gas flowing to the second passage (fourth gas passage) and the volume of the EGR gas flowing to the third passage may be restrained from being unequal or disproportionate from each other. In the flow passage configuration disclosed in Reference 1, the first passage and the communication bore extend orthogonal to each other while the communication bore and each of the second and third passages extend orthogonal to each other.
According to the flow passage configuration disclosed in Reference 1, because the first passage and the communication bore extend orthogonal to each other while the communication bore and each of the second and third passages extend orthogonal to each other, it may be considered that the EGR gas is still easy to flow to the third passage because of inertia of the EGR gas. Thus, it may be considered that the volume of the EGR gas flowing to the second passage is inhibited from effectively increasing according to the flow passage configuration in Reference 1. As a result, imbalance or disproportion between volumes of the EGR gas distributed to the third passage (third gas passage) and to the second passage (fourth gas passage) may not be effectively restrained.
A need thus exists for an intake apparatus which is not susceptible to the drawback mentioned above.